Personally, I don't even think it's about being compliant. Any decent website should be at least renderable in any browser.
NTFS.org is a good example. Sure that "logo bar" on top don't line up correctly on the main page, but at least I can see it and I can see the intended effect. But when a site "requires" a particular browser and don't even load at all, I think there's a problem.
It's not about standards to me, it's about me being able to choose what program I use for what. It's not my lose that your page isn't viewable to me.
Even the Microsoft.com website is usable in Mozilla.
-Ryandor